This paper reviews the use of circuit transfer processes for optoelectronic applications. In this process, a circuit comprising either Si or GaAs devices is removed from its original substrate and is transferred to a second substrate. For active matrix displays, CMOS circuits are transferred in this way to glass substrates, and active matrix liquid crystal displays with pixel format of 1280 by 1024 (with 1000 lines per inch) have been successfully formed. Photovoltaic circuits have also been transferred to glass and to other photovoltaic devices to further the formation of multi-bandgap tandem structures. LED arrays have been formed successfully by this technique as well. This work shows the potential for combining CMOS and III-V circuits to form integrated optical input and output devices, as well as optical power delivery to silicon circuits. We review progress in these areas and suggest new applications of the technology.